It’s easy to forget that Mike McCarthy made big coaching changes on both sides of the ball last January.

McCarthy’s hiring of Mike Pettine gets all the attention, for obvious reasons. He’s a defensive coordinator for an offensive head coach. The defense is his in every way that matters, and he now speaks for that side of the ball. When the Green Bay Packers play the Chicago Bears at Lambeau Field on Sunday, the differences between his approach and Dom Capers’ will be displayed for all to see.

With new (and old) offensive coordinator Joe Philbin, it won’t be so self-evident. The offense and play calling are McCarthy’s. Things probably won’t look all that much different.

Still, Philbin, in a subtler way, could end up having a big influence on the Packers‘ season because of his credibility with McCarthy and experiences gained from six seasons coaching elsewhere in the NFL.

“I think he’ll challenge Mike to have more dialogue,” is how one source who knows both men put it.

In Philbin’s previous run as McCarthy’s coordinator, the five seasons from 2007-11, the Packers finished in the top five in scoring four times. That includes a No. 5 ranking in Aaron Rodgers’ first season as a starting quarterback (2008) and putting up the third-highest scoring season in NFL history (2011).

To attribute those accomplishments to Philbin would, of course, be foolish. Rodgers blossomed into an elite quarterback during that time, and for a couple years there the Packers were uncommonly deep with quality players in the passing game (Greg Jennings, Jordy Nelson, Jermichael Finley, Donald Driver and Randall Cobb). And yes, McCarthy was in the captain’s chair.

But Philbin’s return this year provides a highly-respected voice to offensive game planning plus a broader perspective after his stints as the Miami Dolphins’ coach (2012-15) and the Indianapolis Colts’ assistant head coach-offensive line (2016-17).

That matters, because there’s no escaping the feeling that McCarthy’s offense had gone stagnant the last couple years even if it still was putting up good numbers when Rodgers was healthy. This is where Philbin could make a difference.

His credibility with McCarthy figures to have carried weight when the coach charged his offensive staff to revamp the playbook early in the offseason, and should do the same when the two meet on the weekly game plan during the season. All head coaches need someone they trust to tell them when they’re wrong and occasionally spark creative disagreement.

“I think Mike respects Joe a lot, and there’s a lot of mutual admiration,” Rodgers said in an interview this week. “They’ve coached together for a long time. I’ve been in some of those install meetings to see how they go, and Joe does a great job coming up with ideas, talking through things, throwing stuff out that doesn’t fit or doesn’t work, bringing stuff in when guys have ideas.”

Teams are secretive about their schemes, so nobody is revealing what changed in the Packers’ playbook. But we wonder if we saw a hint of evolution in an otherwise vanilla preseason on a third down in the third quarter last week at Kansas City.

On that play, the Packers lined up two receivers just off tackle on the left side, and when they cleared out after the snap, running back Bronson Hill ran a circle route into the area they vacated. He was wide open for a short touch pass from No. 3 quarterback Tim Boyle and picked up the first down with an easy 12-yard gain. It was a slick play design and something the Packers hadn’t shown in past years.

“(Passing game coordinator) Jim Hostler and Joe have brought some concepts they’ve run from other places,” Rodgers said, “and we’ve put a decent amount of them in the offense, which has been good.”

As offensive coordinator, Philbin is McCarthy’s right-hand man for game planning, responsible for installing the game plan when the offense meets as a group, and scripting the game plan for practice, among other things.

In the group meetings, teaching skills are paramount for relaying the week’s plan. Rodgers thinks Philbin excels in this role, especially at making things easy to remember with mnemonic cues.

“He’s incredible in front of the (offensive) room,” Rodgers said. “Combines his teaching ability with some dry humor that I really respect and appreciate. He’s brought a great energy to us. I’m not sure how it’s going to translate on the field, but he holds everybody accountable.”

The Packers actually have had a lot of change on the offensive side of the ball this year, even if the only major roster move was swapping Jimmy Graham for Jordy Nelson in free agency.

Besides Philbin and Hostler, McCarthy also hired a new quarterbacks coach (Frank Cignetti) and overhauled the playbook. Rodgers has had to learn new play-calling language that sometimes conflicts with the old playbook.

“An extra learning curve,” he said.

In the end, players matter most, so if you’re ranking the impact of the changes on that side of the ball, the Graham signing is first. But Philbin’s return could end up mattering, too.

“Don’t want to stroke (Philbin’s) ego too much, but big fan of his,” left tackle David Bakhtiari said. “I can definitely see how he was a head coach. He’s got complete control as being an offensive coordinator, he knows where everybody’s got to be. You can tell his passion through how he approaches every single meeting, every walkthrough. I feel bad giving him a lot of credit, but he’s as advertised if not better.”

There won’t be any simple way to measure whether Philbin makes much difference for the 2018 Packers. There won’t be any saying for sure.